Persistent abdominal symptoms in returning travellers: clinical and molecular findings

Background Persistent abdominal symptoms (PAS) are the leading cause of post-travel morbidity although there is a paucity of evidence concerning the aetiology of this condition. Recently molecular methods for protozoa detection in stool have been introduced. Herein, we describe the clinical aspects and the prevalence of gastrointestinal protozoa in returning travellers with PAS. Methods From 2017 to 2019, clinical information and stool specimens from returning travellers with PAS were analysed for the presence of parasites using the Allplex-GI-Parasite-assay. Stool findings from symptomatic patients without a travel history were used as a comparator. Results During the 2-year study, 203 stool specimens from returning travellers were analysed. The median duration of symptoms before seeking care was 6 months, the most common symptoms were fatigue (79.2%), abdominal pain (75.7%) and loose stool (70.8%). Most of travellers had returned from Asia (57.6%), mainly from the Indian-subcontinent and only 52.6% were backpackers. Altogether, 36.9% samples were positive for protozoa, with Blastocystis hominis being the most common (26.6%) in samples, followed by Dientamoeba fragilis (18.7%), Giardia lamblia (3.0%) and Cryptosporidium spp (0.5%). The former two were dominant in all regions. In all cases but one, G. lamblia was acquired, but one were acquired in the Indian subcontinent (odds ratios 16.9; 95% confidence intervals: 1.9-148.3). Entamoeba histolytica was not detected. The demographic characterization of the 1359 non-travellers was comparable with the travellers. Among them D. fragilis was the most common followed by B. hominis, which was significantly less frequent compared among the travellers (16.7% vs 26.6%, P < 0.001). Average Cycle threshold values for each stool parasites were comparable between the two groups. Conclusion Among returning travellers with PAS, more than one-third were positive for gastrointestinal protozoa. A low rate of giardia was found and no E. histolytica while B. hominis followed by D. fragilis were the dominant findings. Further studies are required to better understand the role of these protozoa in PAS.